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Modes of Operation of IDS/IPS

Snort

Snort, a popular Network Intrusion Detection System (NIDS), operates in three primary modes, each tailored for specific purposes:

Sniffer Mode:

  • Function: Primarily used for capturing and inspecting network traffic data.
  • Activation Flag: Invoked using the -v flag with the command (e.g., snort -v).
  • Output: Displays captured packets in real-time on the console, providing a glimpse into the network activity.
  • Application: Useful for understanding network behavior, troubleshooting connectivity issues, or gaining insights into data flow.

Packet Logger Mode:

  • Function: Like sniffer mode, it captures network traffic.
  • Activation Flag: Enabled using the -l flag (e.g., snort -l).
  • Output: Instead of displaying packets on the console, it logs them to a specified disk location.
  • Application: This mode facilitates storing captured packets for further analysis with different tools or manual inspection later.

Network Intrusion Detection System (NIDS) Mode:

  • Function: The core functionality of Snort lies in this mode.
  • Activation Flag: It is Initiated using either the -c flag or specifying the configuration file path (e.g., snort -c snort.conf).
  • Process:
    • Monitors network traffic based on predefined rules in a configuration file.
    • Analyzes packets against these rules, searching for suspicious patterns or activities that might indicate potential security threats.
  • Alerting: If a packet matches a rule, Snort can be configured to:
    • Generate alerts and notify the administrator about potential intrusions. (IDS)
    • Block the malicious traffic, preventing further harm to the system. (IPS)
  • Application: This mode is crucial for actively safeguarding the network by detecting and responding to potential security risks.

Suricata

Unlike Snort, which offers distinct operational modes, Suricata primarily functions in a single comprehensive mode that combines the functionalities of:

  • Packet Capture: Similar to Snort's sniffer mode, Suricata captures network traffic using various methods like pcap (packet capture library), libpcap, or specific capture interfaces.

  • Packet Inspection: Suricata analyzes the captured packets using a multi-threaded approach, dissecting them layer-by-layer to extract relevant information.

  • Rule Matching: It employs a rule engine that compares the extracted data against a predefined rule set. These rules can identify suspicious patterns or activity indicative of potential threats.

  • Action Triggering: Based on the rule matches, Suricata can be configured to take various actions:

    • Alerting: Informing the administrator about potential threats through logs or notifications.
    • Logging: Recording details of suspicious activity for further analysis.
    • Packet Dropping: Actively blocking malicious traffic, preventing it from reaching the intended target.

Additional Considerations:

  • IPS (Intrusion Prevention System) Mode: While Suricata primarily operates in this comprehensive mode, it can prioritize specific actions. Enabling IPS mode emphasizes packet dropping over just generating alerts, offering a more proactive approach to security.    
  • Customization: Suricata's behavior can be fine-tuned through configuration options. This allows tailoring actions based on the severity of threats and network security policies.

Zeek

Zeek's specific operational modes are limited.

  • Core Functionality: Unlike Snort and Suricata, Zeek (previously Bro) primarily focuses on network traffic analysis rather than solely acting as a Network Intrusion Detection System (NIDS).

  • Packet Capture and Processing: Zeek captures network traffic and preprocesses it for further analysis.

  • Deep Packet Inspection: Zeek delves deeper into the captured traffic, analyzing headers and payload data.

  • Rule-Based Analysis: While specific rule sets might be used within Zeek, its approach often differs from Snort's rule-based triggering of actions. Zeek emphasizes threat hunting and traffic analysis, providing insights and data for security teams to investigate and identify potential issues.

Distinguishing Factors:

  • Focus on Analysis: Unlike Snort and Suricata's emphasis on real-time intrusion detection and blocking, Zeek prioritizes in-depth analysis and threat-hunting capabilities.

  • Alerting: Zeek can generate alerts based on its findings, but it doesn't directly focus on real-time blocking actions.